1. Field of the Invention
The present invention relates to a process for lapping the backside of a wafer with an ultraviolet tape attached to the front side thereof, and, more particularly, to a method for processing the backside of a wafer which is intended to carry out a lapping process for efficiently reducing damage of a wafer due to inherent adhesive stress of an ultraviolet tape used for protecting a circuit pattern formed on the front side of the wafer as well as a grinding process, thereby improving processing efficiency.
2. Description of the Prior Art
In a conventional process for manufacturing semiconductor products such as diodes, transistors and the like, a process for treating the backside of a wafer causing it to have a predetermined thickness (for example, about 200 μm) is involved. The process for treating the backside of a wafer comprises a grinding procedure or a lapping procedure. In the case of processing the backside of wafer, it is very important to protect a circuit pattern formed on the front side of the wafer.
In a conventional method for protecting the front side of a wafer, a process for applying a photoresist layer to the front side of a wafer to protect the pattern or a process for attaching a protecting tape to the front side of a wafer has been used.
A method for applying a photoresist layer to the front side of a wafer has an advantage in that it is capable of protecting the front side of a wafer reliably. That is, such a method for applying a photoresist layer can efficiently prevent damage to a wafer since the photoresist layer is hardly deformed by condition of a lapping jig on which the front side of the wafer is placed. Therefore, the method of applying a photoresist layer is easily adopted in a lapping process.
However, the method of applying a photoresist layer has disadvantages in that a substantial period of time is required to carry out the whole process and the process is considerably complicated because the process for coating a photoresist layer adapted to protect the front side of a wafer and a process for removing the photoresist layer after completion of a lapping process are required. For example, since an exposing process and a hard-baking process are involved in the process for coating a photoresist, and a wafer must be dipped into photoresist strip solution for 40 minutes and then washed in order to remove the photoresist layer after completion of the lapping process, the process becomes complicated. In addition, the process also has a problem in that a lapped thin wafer can be easily broken during elimination of the photoresist layer.
For overcoming the above disadvantages occurring in the method using a photoresist layer, a method for attaching a tape to the front side of a wafer has been used to protect a pattern formed to the front side. As such a tape for protecting the front side of a wafer, an ultraviolet tape, to which an adhesive containing ultraviolet curing agent is applied, is predominantly used. According to the conventional method for attaching a tape adapted to protect a pattern, a tape is attached to the front side of a wafer, a backside of the wafer is processed, and the tape is removed from the front side of the wafer.
Although the process for treating the backside of a wafer with an ultraviolet tape attached to the front side thereof can be more easily achieved as compared with the process with a photoresist layer, it has a serious drawback in that the process cannot be connected with a lapping process. That is, the front side of a wafer, to which an ultraviolet tape is attached, must be coupled to a lapping jig, but the ultraviolet tape attached to the lapping jig is apt to be deformed by condition of the lapping jig, and the thin wafer may be easily broken by inherent adhesive stress of the ultraviolet tape during a lapping process.
Accordingly, the process for treating the backside of a wafer with ultraviolet tape attached to the front side thereof can adopt only a grinding process in which a wafer is held under vacuum condition. Ultimately, since the process can carry out only a grinding process, it is difficult to expect a fine surface condition, which can be achieved by a lapping process.
As mentioned above, the process for treating the backside of a wafer with a photoresist layer applied to the front side thereof complicates a whole process by process for applying and removing a photoresist layer. Also, the process has a disadvantage in that the wafer is liable to be broken during a process relating to the photoresist. On the other hand, a process for treating the backside of a wafer is difficult to be adopted in a lapping process because of adhesive stress and thus deformation of an ultraviolet tape.